1. Field of the Invention
The present invention relates to display devices, display methods therefor, and electronic apparatuses. In particular, the present invention relates to a display device, a display method therefor, and a display device which display images by utilizing and modulating light of light sources.
2. Description of the Related Art
Color image display system can be broadly divided into two systems according to an additive color mixing method. A first system is additive color mixing based on a spatial color mixing principle. Specifically, sub-pixels of the three primary colors of light, namely, R (red), G (green), and B (blue), are arranged in a plane at a high density, and the individual color lights are made indiscriminable taking advantage of the spatial resolution of the human eye and are mixed to provide a color image. This first system is employed by a majority of currently commercially available systems, such as CRT (cathode ray tube) systems, and PDP (plasma display panel) systems, and liquid crystal systems.
When the first system is used to configure a display device of a type that displays images by modulating light from light sources (a backlight), for example, a display device that uses non-self-luminous elements (typified by, e.g., liquid crystal elements) as modulation elements, some problems arise. Specifically, such a display device typically requires, for a single screen, three drive circuits that drive sub-pixels so as to correspond to R, G, and B colors, respectively. In addition, such a display device typically requires an RGB color filter. Because of the presence of the color filter, light from the light sources is absorbed by the color filters and thus the light utilization efficiency is reduced to one third.
A second system is additive color mixing based on temporal additive color mixing. More specifically, the RGB primary colors of light are divided along a time axis and plain images having the respective primary colors are sequentially displayed over time (i.e., are time-sequentially displayed). The screens are switched at such a speed that the switching thereof is unperceivable taking advantage of the temporal resolution of the human eye, so that color light is made indiscriminable by temporal color mixing based on the eye's integration effect in the time direction, and a color image is displayed through temporal color mixing.
When the second system is used to configure a display device that uses non-self-luminous elements (typified by, for example, liquid crystal elements) as modulation elements, there are advantages as follows. For example, since a state in which color displayed on one screen at the same time is a homogenous color is obtained, it is possible to eliminate a spatial color filter for discriminating, for each pixel, a color to be displayed on the screen.
Further, with respect to a monochrome display screen, light of the light sources is switched to homogenous-color light and individual screens are switched at such a speed that the switching thereof is unperceivable. In synchronization with back-light (based on the eye's integration effect) being switched to, for example, a monochrome color of R, G, and B, the display image is switched in response to an R signal, G signal, and B signal. Thus, the driving can be performed by only one drive circuit.
In addition, since the color screening is switched over time and a color filter can be eliminated, the second system has an advantage of reducing the loss of the amount of light passage, as described above. Thus, nowadays, the second system is mainly utilized as a modulation system for high-luminance high-heat light sources, in which a reduction in the amount of light tends to cause critical thermal loss, for projectors (projection display systems) and so on. The second system also has an advantage of high light-utility efficiency, and thus various studies are under way.
The second system, however, has a significant drawback in terms of vision. Specifically, the basic display principle of the second system is that, as described above, the screens are switched at a speed at which the switching thereof is unperceivable utilizing the temporal resolution of the human eye. However, the RGB images that are sequentially displayed according to the sequence of elapsing time do not mix with each other properly because of complicated factors, such as a limitation in the optic nerves for the eyeball and sensations of image recognition of the human brain. This can cause a display phenomenon called “color breakup (or color breaking)” by which an image in each primary color is seen as an afterimage or the like and with which the observer feels very unpleasant, particularly, when a low-purity image such as a white image is displayed or when he or she keeps track of a moving object displayed on the screen.
Various approaches have been proposed to overcome the drawbacks of the second systems described above. For example, there is a drive system for reducing the amount of color breakup by performing sequential color driving without use of a color filter and inserting a white display frame to sequentially apply stimulus to spectral energy on the retina.
For example, Japanese Unexamined Patent Application Publication No. 2008-020758 discloses a technology for reducing the amount of color breakup. In the technology, a field in which white light components are to be mixed in a white-color component period is provided in each field of an RGB field sequential system.
As another example of the related art proposed to prevent color breakup, Japanese Unexamined Patent Application Publication No. 2002-318564 discloses a technology in which white components are extracted and W (achromatic color) fields are additionally inserted into a sequence of fields “RGBRGB . . . ” to provide a sequence of four fields “RGBWRGBW . . . ”. For example, Japanese Unexamined Patent Application Publication No. 2003-248462 disclose a technology for preventing color break by extracting image information and varying the coordinates of the color origin points of the primary colors (basic colors) to be processed.